very basic timing sequence. Please help

[dzilber]

Hi,
  This is a very simple question. I want to have a graph display real time data, while a sequence of LEDS light up for variable amounts of time. I cant simply use a time delay because then the graph pauses as well. I think the best course is to use a timing sequence, but these seem very complicated. How can I configure the VI so that first one LED turns on, then after 4 seconds turns off, so another can turn on, etc, all while the graph displays data?

   I truly appreciate your help.
  David

Message Edited by dzilber on 04-09-2007 09:54 PM

[Jarrod_S.]

Try two loops. That's part of the beauty of LabVIEW. Two loops not connected by a wire from one loop to the other will run in parallel. One for the graph data and one to run the sequence of LEDs. No need for a timed sequence if you want to keep it simple. The two loops can run in parallel and different rates to handle separate tasks.

[ian_fung]

Here is a quick example of two loops that I have posted in forum of China area. Cheers!

[dzilber]

Message Edited by dzilber on 04-10-2007 06:08 PM

[dzilber]

Well I dont know how I could run two loops at the same time for my application because The graphed data must happen precisely at the same moment the LEDS fire. Im pretty sure I should use a timed sequence structure, I just dont know how, and cant find any good examples.

Ian, youre response is helpful but I think its in the same direction as Jarrod's. I need two events to happen simultaneously, with one of the two occurring at a specified rate.

[RavensFan]

You don't want a timed sequence structure.  You want timed loops.

It is unclear as to what you mean by "while a sequence of LEDS light up for variable amounts of time".  What is variable about the times?

You could probably do all that you want in a single timed loop.  Allow the graph to update at every iteration.  Use the loop counter, or even the timer functions (is current time >= to start time + 4 seconds?) to determine when to turn on or off the LED's.

If you use 2 parallel timed loops and set the properties of the loops to maintain phase, each iteration of each loop shoud occur nearly simultaneously.

Another possibility is to use 2 loops and use notifiers, rendezvous's, or other synchronization functions to keep the loops operating together.  But from your description, I don't think you would need to go that advanced.

[dzilber]

Hmm, that sounds like its what Im looking for. Do you have any examples?

Specifically I have a noise generator that must create a constant signal at a constant rate. When a certain button is pushed, the noise generator is swapped with a signal generator. Meanwhile, a sequence of LEDS must fire, each for say 2 seconds. Then the system resets. The problem with making each LED stay on for 2 seconds at a time using the wait function is that it makes the graph pause for 2 seconds as well. See my problem?

[LabViewGuruWannabe]

Howdy,

Instead of a Wait, try using the Elapsed Time Express VI. Or, if you don't have that, do it the manual way using the Get Date/Time.

Get Start Time (at the beginning)
Get Current Time (inside the loop)
Elapsed Time = Current Time - Start Time
If Elapsed Time < Stop Time, Turn LED ON
If Elapsed Time >= Stop Time, Turn LED OFF

Repeat as necessary for all LED's.

I can make a block diagram if you need it, but I think you'll get the idea.

B-)

[RavensFan]

Try this.

New data is created every 1/10 second and updated on an XY graph.  Every 20 iterations (2 seconds), the 2 LED's toggle.